a) Technical Field
The present invention relates to an electric motor having a shaft and a bearing holder partly projecting out of the motor main body such as a capstan motor.
b) Background Art
An electric motor having a shaft and a bearing holder partly projecting out of the motor main body such as a capstan motor is normally used for the tape feeding system of a video tape recorder (VTR). FIG. 5 of the accompanying drawings illustrates a capstan motor of a known type.
Referring to FIG. 5, a shaft 4 is received by a bearing 3, which is in turn held by a bearing holder 2 rigidly fitted to a disc-shaped substrate 1 so that a rotor 5 fitted to the shaft 4 and disposed vis-a-vis the lower surface of the substrate 1 can rotate around the shaft 4. The bearing holder 2 is partly projecting out of the upper surface of the substrate the side opposite to the one where the rotor 5 is arranged to form a frustro-conical portion 2a, from which the shaft 4 is further projecting by a given distance to constitute a capstan shaft. The illustrated motor is a so-called direct drive type and the bearing holder 2 of the motor is rigidly fitted to a chassis while it is firmly holding the shaft 4.
FIG. 6 of the accompanying drawings illustrates a known belt driving type motor comprising a shaft and a flywheel 7 fitted to its lower end and a belt 8 arranged to partly surround the outer periphery of the flywheel 7. In this belt driving type motor, again, a bearing holder 2 is rigidly fitted to a chassis while it is firmly holding a shaft 4.
When an upper portion of the motor shaft is used as a capstan shaft, it provides a reference speed for continuously feeding a tape to a recording or reproducing head and pinch rollers and other components of a tape feeding system are arranged by referring to the capstan shaft. Besides, a control head, an audio head and other components of a signal retrieving system as well as a number of components of other systems of a video tape recorder are arranged near the capstan shaft. These and other parts of a video tape recorder other than the motor are, in most cases, securely fitted to a chassis separately and independently from the motor.
When components of a video tape recorder other than a motor are rigidly but independently fitted to a chassis, however, they tend to be fitted differently from each other in terms of working standards so that system and a signal retrieving system may be mounted according to different standards, giving rise to a problem of inadequate mounting precision. This problem has to be seriously addressed if a video tape recorder is to be realized with excellent precision. Moreover, the number of components has been increasing in recent years which tends to lower the productivity and raise the manufacturing cost of such a video tape recorder.